Vacuum raising

[smahsan]

Hi,
I want to know that why do we Start the CW pumps(circulating water system)if we are going to raise the vauum in the condenser?.How the cooling is helpfull during condenser vacuum raising?
As same as in the Desalination plant we spray the water in the effects and as wel as we start the vacuum raising even the main steam is not admitted in the first effect of multi evaporated films type units. My two basic question are as under.
Why we spray the water even there is no Heat?
What is the advantage of water spray or cooling with vacuum raising?
Regards
Ahsan

 

[imok2]

In a closed container that has been heated with steam it's a given that as the container is cooled, a higher vacuum will develop. This is because as the steam condenses (because of the cooling effect) a higher vacuum will occur. This is why you install a vacuum relief valve on steam equipment when you stop the flow of steam.

 

[danberry]

It is not necessary with a cold system. If there is hot water present, cooling will condense flash steam that would slow the process of removing non-condensibles.